Could Caffeine Kill You?

You probably saw the headlines last week: Five dead from drinking Monster Energy drinks. In the past, herbal supplements like ephedrine—an ingredient in Monster—have taken the blame for causing heart attacks, but could the real killer this time have been caffeine?

Considering investigators found levels of the stimulant to be seven times higher in the drink than in a 12-ounce can of soda, it’s quite possible.

But before you call it quits with caffeine, know that death by the stimulant is incredibly rare, says Julie Kennel, Ph.D., RD, a professor at Ohio State University. The five people who died likely consumed 1.6 times the daily serving size of the drink within minutes and were sensitive because of their young age—one was only 14 years old—and smaller body size, says Kennel. Just like with alcohol, the smaller you are, the more susceptible you may be to caffeine.

So breathe easy, javaheads—your daily cuppa Joe shouldn't mess with your health. (In fact, you can even Protect Your Heart with Coffee.) But know this: Caffeine, even in moderation, can have some nasty side effects, says Jim Lane, Ph.D., a psychophysiology professor at Duke University. Here are a few to watch out for.

Instant onset diarrhea
It’s the classic weird caffeine side effect, but it’s also the least understood of them all, Lane says. Researchers do have a hunch: Caffeine causes contractions in your large intestine, which send excrement down the pipes and you running to the toilet. Stress could be to blame, too, says Lane. Your body’s stress hormones and caffeine each activate your intestines, so when both levels are elevated, it can cause quick, powerful contractions with disastrous results.

High blood pressure
A single cup of coffee might not make a noticeable difference, but the high amounts of caffeine in an energy drink like Monster will spike your blood pressure, says Lane. And if you consume such drinks regularly—we're looking at you, college students—your blood pressure will remain elevated. (And unless you're a fan of developing heart disease, that's not a good thing.) Lane says caffeine may essentially impersonate adrenaline, a hormone that can spike blood pressure by causing the muscle lining your arteries to contract. (See 5 more things that send your blood pressure through the roof.)

High blood sugar
If you're at risk for type 2 diabetes—for example, you're overweight and inactive—your afternoon energy drink may hasten the onset of symptoms. Because of its antioxidant properties, coffee generally reduces your risk of type 2 diabetes by improving your glucose metabolism. But in people who are diabetic or at risk for the disease because of weight and inactivity, the negative effects of caffeine outweigh coffee's antioxidant punch, which most energy drinks lack to begin with. In a 2008 study, researchers found that after taking a 250 mg caffeine pill, the blood sugar levels in diabetics increased 8 percent. For diabetics and those at risk for the disease, caffeine decreases their body’s sensitivity to insulin—a hormone vital for moving glucose into your cells, Lane explains. And when your body can’t process sugars as well, they pool in your blood, causing inflammation and damage.

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